I recently had to test various icons with different backgrounds and I couldn't find anything useful. My only option was to load the icon in Xcode, build and run and restart the springboard. Not a great solution, takes too much time. With this template, you can simply drop your icon and see how it would look in the home screen. I also included some default wallpapers so you can test different lighting and colors and see what is the best icon.
Here's the PSD file: https://www.dropbox.com/s/p7xrr5661mhls9i/iOS7HomeScreenTestIcons.psd
Enjoy!
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